Purification of Several Salt Marsh Plants to the Coastal Wetlands in the Estuary of Yellow River

The paper compared the differences between above ground and underground biomass of four types of plants.The heavy metals(Cu,Zn,Cd,Cr,Pb,As,Hg)and nutrients(TN,TP)content in tissues of four maturity plants were detected,and their enrichment coefficient and transfer coefficient were calculated.The results showed that Suaeda salsa had the largest concentrated capacity on Cu,Zn,Pb,As and Phragmites australis was larger on the Cd,Hg than other plants.Considering the purification of four plants,the effect on the restoration of heavy metal pollution was better if we harvested Phragmites australis and Suaeda salsa.Four plants had a larger difference in absorption capacity of nitrogen and smaller absorption of phosphorus.Phosphorus uptake was significantly smaller than nitrogen.Harvesting Phragmites australis and Suaeda salsa can reduce total nitrogen and phosphorus content of the wetland,while harvesting Spartina alterniflora and Typha orientalis can reduce total phosphorus content.

Plant salt tolerance and Na^+ sensing and transport

Salinity is a global challenge to agricultural production. Understanding Na^+ sensing and transport in plants under salt stress will be of benefit for breeding robustly salt-tolerant crop species. In this review, first, possible salt stress sensor candidates and the root meristem zone as a tissue harboring salt stress-sensing components are proposed. Then,the importance of Na^+ exclusion and vacuolar Na^+ sequestration in plant overall salt tolerance is highlighted. Other Na^+ regulation processes, including xylem Na^+ loading and unloading, phloem Na^+ recirculation, and Na^+ secretion, are discussed and summarized.Along with a summary of Na^+ transporters and channels, the molecular regulation of Na^+ transporters and channels in response to salt stress is discussed. Finally, some largely neglected issues in plant salt stress tolerance, including Na^+ concentration in cytosol and the role of Na^+ as a nutrient, are reviewed and discussed.

Advanced Backcross QTL Analysis for the Whole Plant Growth Duration Salt Tolerance in Rice(Oryza sativa L.)

Salinity is a major factor limiting rice yield in coastal areas of Asia. To facilitate breeding salt tolerant rice varieties, the wholeplant growth duration salt tolerance（ST） was genetically dissected by phenotyping two sets of BC2F5 introgression lines（ILs） for four yield traits under severe natural salt stress and non-stress filed conditions using SSR markers and the methods of advanced backcross QTL（AB-QTL） analysis and selective introgression. Many QTLs affecting four yield traits under salt stress and nonstress conditions were identified, most（〉90%） of which were clustered in 13 genomic regions of the rice genome and involved in complex epistasis. Most QTLs affecting yield traits were differentially expressed under salt stress and non-stress conditions. Our results suggested that genetics complementarily provides an adequate explanation for the hidden genetic diversity for ST observed in both IL populations. Some promising Huanghuazhan（HHZ） ILs with favorable donor alleles at multiple QTLs and significantly improved yield traits under salt stress and non-stress conditions were identified, providing excellent materials and relevant genetic information for improving rice ST by marker-assisted selection（MAS） or genome selection.

Plant assemblage and diversity variation with human disturbances in coastal habitats of the western Arabian Gulf

Knowledge about plant diversity along disturbance gradients is essential for conservation and management of fragmented coastal habitats.This study examined the effects of human disturbance intensity in coastal habitats of Kuwait on diversity,composition,identity and assemblage of vascular plant species.Plant survey data from 113 plots （5m×5m each） were randomly selected in 51 sites at coastal fragmented habitats at three levels of disturbance intensities （high,moderate and low） and were statistically analyzed.The results revealed that about 76% of the recorded species are considered threatened species in Kuwait,most of which are being lost in high disturbed habitats.Disturbance led to the dominance of Zygophyllum qatarense,Cornulaca aucheri and Salsola imbricata,which are species of disturbance indicators.Richness,total plant cover and species diversity were higher in moderate and low disturbed habitats than in high disturbed habitats.Beta diversity between high and low disturbed habitats was higher than either between high and moderate,or between moderate and low disturbed habitats.Cluster analyses showed statistically significant differences in composition of plant assemblages,which indicate high beta diversity between the habitat types.Intensive urbanization and industrialization are among the most serious threats that contribute to declines in biological diversity and rapid fragmentation of coastal habitats in Kuwait.Establishing protective enclosures in the disturbed habitats,planting endangered and vulnerable species,and establishing a natural reserve at Nuwaiseeb are recommended conservation actions to avoid loss of the fragmented coastal habitats and to facilitate restoration of native plants.

Insights into plant salt stress signaling and tolerance

Soil salinization is an essential environmental stressor,threatening agricultural yield and ecological security worldwide.Saline soils accumulate excessive soluble salts which are detrimental to most plants by limiting plant growth and productivity.It is of great necessity for plants to efficiently deal with the adverse effects caused by salt stress for survival and successful reproduction.Multiple determinants of salt tolerance have been identified in plants,and the cellular and physiological mechanisms of plant salt response and adaption have been intensely characterized.Plants respond to salt stress signals and rapidly initiate signaling pathways to re-establish cellular homeostasis with adjusted growth and cellular metabolism.This review summarizes the advances in salt stress perception,signaling,and response in plants.A better under-standing of plant salt resistance will contribute to improving crop performance under saline conditions using multiple engineering approaches.The rhizosphere microbiome-mediated plant salt tolerance as well as chemical priming for enhanced plant salt resistance are also discussed in this review.

Soil Organic Carbon Contents and Stocks in Coastal Salt Marshes with Spartina alterniflora Following an Invasion Chronosequence in the Yellow River Delta,China

Plant invasion alters the fundamental structure and function of native ecosystems by affecting the biogeochemical pools and fluxes of materials and energy. Native(Suaeda salsa) and invasive(Spartina alterniflora) salt marshes were selected to study the effects of Spartina alterniflora invasion on soil organic carbon(SOC) contents and stocks in the Yellow River Delta. Results showed that the SOC contents(g/kg) and stocks(kg/m^2) were significantly increased(P < 0.05) after Spartina alterniflora invasion of seven years, especially for the surface soil layer(0–20 cm). The SOC contents exhibited an even distribution along the soil profiles in native salt marshes, while the SOC contents were gradually decreased with depth after Spartina alterniflora invasion of seven years. The natural ln response ratios(Ln RR) were applied to identify the effects of short-term Spartina alterniflora invasion on the SOC stocks. We also found that Spartina alterniflora invasion might cause soil organic carbon losses in a short-term phase(2–4 years in this study) due to the negative Ln RR values, especially for 20–60 cm depth. And the SOCD in surface layer(0–20 cm) do not increase linearly with the invasive age. Spearman correlation analysis revealed that silt + clay content was exponentially related with SOC in surface layer(Adjusted R^2 = 0.43, P < 0.001), suggesting that soil texture could play a key role in SOC sequestration of coastal salt marshes.

Unraveling salt stress signaling in plants

Salt stress is a maior environmental factor limiting plant growth and productivity. A better understanding of the mechanisms mediating salt resistance will help researchers design ways to improve crop performance under adverse environmental conditions. Salt stress can lead to ionic stress, osmotic stress and secondary stresses, particularly oxidative stress, in plants. Therefore, to adapt to salt stress, plants rely on signals and pathways that re-establish cellular ionic, osmotic, and reactive oxygen species （ROS） homeostasis. Over the past two decades, genetic and biochemical analyses have revealed several core stress signaling pathways that participate in salt resistance. The Salt Overly Sensitive signaling pathway plays a key role in maintaining ionic homeostasis, via extruding sodium ions into the apoplast. Mitogenactivated protein kinase cascades mediate ionic, osmotic, and ROS homeostasis. SnRK2 （sucrose nonfermenting l-related protein kinase 2） proteins are involved in maintaining osmotic homeostasis. In this review, we discuss recent progress in identifying the components and pathways involved in the plant＇s response to salt stress and their regulatory mechanisms. We also review progress in identifying sensors involved in salt-induced stress signaling in plants.

Fluorescence characterization and microbial degradation of dissolved organic matter leached from salt marsh plants in the Yellow River Delta

Aims Salt marsh vegetation is an important contributor of dissolved organic matter(DOM)to coastal waters.The dynamics of DOM leaching from different marsh plants,however,have not been well studied or compared.Methods In this study,we conducted laboratory experiments to investigate the processes of DOM leaching from three common marsh plants(Phragmites australis,Suaeda salsa and Aeluropus littoralis)collected from the Yellow River Delta(YRD)salt marsh in October 2016.The YRD is one of the largest and most well-protected coastal ecosystems on the east coast of China.Important Findings We found that the plant leaves released DOM at much higher concentrations than the plant roots or stems,as measured by the dissolved organic carbon(DOC)and dissolved nitrogen(DN).On average,15%of the biomass C and 30%of the biomass N were released from the plant leaves as DOC and DN during the 27-day incubation period.The DOM released from the plants was very labile,and 92.4%-98.1%of the DOC and 88.0%-94.6%of the DN released from the plants were consumed by bacteria during the 27-day incubation period.The fluorescence characteristics of the plant-released DOM indicated that chromophoric dissolved organic matter was a major fraction of the DOM and that protein-like components were the primary organic fractions released from the plants.Bacterial degradation altered both the fluorescence properties and the chemical composition of the DOM.The results of the laboratory experiments were well supported by the field investigation,which indicated that a large amount of DOM was outwelled from the YRD salt marshes in late autumn.Our study suggests that the DOM released from the biomass of salt marsh plants provides an important source of both DOC and DN for marsh and coastal waters.The highly labile DOC and DN provide essential food sources to support microbial communities in the YRD salt marsh and adjacent coastal waters.

Invasive Spartina alterniflora accelerates the increase in microbial nitrogen fixation over nitrogen removal in coastal wetlands of China

Salt marsh plants play a vital role in mediating nitrogen(N)biogeochemical cycle in estuarine and coastal ecosystems.However,the effects of invasive Spartina alterniflora on N fixation and removal,as well as how these two processes balance to determine the N budget,remain unclear.Here,simultaneous quantifications of N fixation and removal via^(15)N tracing experiment with native Phragmites australis,invasive S.alterniflora,and bare flats as well as corresponding functional gene abundance by qPCR were carried out to explore the response of N dynamics to S.alterniflora invasion.Our results showed that N fixation and removal rates ranged from 0.77±0.08 to 16.12±1.13 nmol/(g·h)and from 1.42±0.14 to 16.35±1.10 nmol/(g·h),respectively,and invasive S.alterniflora generally facilitated the two processes rates.Based on the difference between N removal and fixation rates,net N_(2)fluxes were estimated in the range of-0.39±0.14 to 8.24±2.23 nmol/(g·h).Estimated net N_(2)fluxes in S.alterniflora stands were lower than those in bare flats and P.australis stands,indicating that the increase in N removal caused by S.alterniflora invasion may be more than offset by N fixation process.Random forest analysis revealed that functional microorganisms were the most important factor associated with the corresponding N transformation process.Overall,our results highlight the importance of N fixation in evaluating N budget of estuarine and coastal wetlands,providing valuable insights into the ecological effect of S.alterniflora invasion.

Soil Salinity Changes Under Cropping with Lycium barbarum L.and Irrigation with Saline-Sodic Water

In order to utilize the wasted saline-sodic soils under shallow groundwater condition, a 3-year field study was carried in a field cropped with Lycium barbarum L. and irrigated by drip irrigation with saline groundwater under the water table depth of 30-40 cm in the northern Yinchuan Plain, China. Effects of cropping duration （one, two, and three years） on soil salinity, soil solution composition, and pH in three adjacent plots were investigated in 2008. Results showed that a high irrigation frequency maintained high soil water potential and subsequently facilitated infiltration and downward movement of water and salt in the crop root zone. Salt accumulated on the edges of the ridges, and soil saturated-paste electrical conductivity （ECe） was higher in the edge. Concentrations of Na^＋, Ca^2＋, Mg^2＋, Cl^-, and SO24^- in the soil increased with the soil depth as did the ECe, while HCO3 and pH had a relative uniform distribution in soil profile. As planting year increased, the ECe and soil salts in the field had a decreasing tendency, while in the root zone they decreased immediately after irrigation and then remained relatively stable in the following growing seasons. HCO3 and pH had little change with the planting year. Results suggested that the application of drip irrigation with saline water could ameliorate saline-sodic soil and provide a relatively feasible soil environment for saline-sodic soils with shallow groundwater.